While she was managing the affairs at the prosperous M&H, Mary did not cease being a mother with a real concern in the growth of her children. She in particular developed a unique and abiding relationship with her first son Edward. He enrolled in the University of Wisconsin in 1908 to study mathematics and eventually attained a doctorate in the field from the University of Kansas. During these years, Mary regularly wrote letters to her son showing her heartfelt concern for his well-being.

“Be careful to be cooking something when you use your kettle, it may set fire to your table otherwise! With much love, Mother.” (3 November 1909)

Mary’s letters to her son also interestingly reveal that the two were capable of interacting on an intellectual level. For instance, they often discuss the technicalities of mining and science of chemistry.

“Herman wants to go down in the mine with you. The drilling in the bottom has come out satisfactorily—there is over 100 feet of shale over the coal fortunately—between 30-40 feet of gravel above, and 40-55 feet of clay above that, [-------] under the river also probably—The furnace will probably be ready in about two weeks—perhaps you would like to be there. The kiln is doing very well.” (4 February 1912)

“I hope you will look about for the Zinc Chloride at Grasselli plant [East Chicago]. The Cadmium they probably make at Cleveland.” (11–12 March 1912)

When Edward was choosing a graduate school to attend, Mary provided her own advice on the matter.

“I wish you would think about Cambridge a little more. Mr [Philip E. B.] Jourdain [British editor of The Monist] does not live in Cambridge itself—about 4 miles away, at Girton, he speaks of ”Trinity College” & through him you would meet real English people, whom it would be a pleasure to know. The Cavendish Laboratory for physics at Cambridge is one of the celebrated ones of the world.” (11–12 March 1912)

Edward eventually returned to La Salle joining his mother in caring for the family business and following his grandfather’s entrepreneurial footsteps. Working side by side with his mother, he served as the secretary of M&H, and, in 1916, he founded the Carus Chemical Company upon teaching himself to manufacture potassium permanganate. The company went on to become the sole U.S. supplier of the chemical and the biggest supplier in the world. In addition to sharing his family’s interests in science and industry, Edward appears to have shared his mother’s, father’s, and grandfather’s philanthropic concerns with education. For a period he served as a board member of the La Salle-Peru High School.